Particle Mixture

ABSTRACT

The invention relates to a particle mixture and the stabilization of a homogeneous distribution of these particles in the mixture.

The invention relates to a particle mixture and the stabilization of these particles in the mixture.

For protecting articles, such as e. g. documents of value, high-quality branded goods, etc. against forgery, frequently luminescent substances are used. These substances are typically processed in the form of powdered pigments, like described in EP 0 659 935 A2.

To increase protection from forgery it was suggested in WO 00/71363 to use mixtures of several luminescent substances, in particular also as to be able to produce codings. The coding can e. g. consist in the different luminescent substances being present in different amounts in the mixture.

Furthermore WO 02/078964 discloses a color coding for an object, wherein particles, which have different colors and which are not perceptible to the naked human eye, form a coding.

For the user it is decisive that the coding is uniform throughout the mixture and does not change within the mixture.

Particularly during the transport of larger packaging units from the producer to the customer there is frequently the problem that particle mixtures, which contain e. g. particles with different diameters, are segregated by jarring movements, since the smaller particles tend to migrate in the direction of the bottom of the packaging, whereas the bigger particles accumulate on the surface.

Proceeding from this state of the art, it is the problem of the invention to minimize or to prevent the segregation of powdered mixtures of different particles.

The solution to this problem can be found in the independent claims. Developments are subject of the subclaims.

According to the invention a particle system is provided, which comprises a container and a particle mixture disposed in the container. At least a part of the particles in the mixture differs in at least one measure from the rest of the particles, wherein the container has at least one means which essentially prevents the spatial movement of the particles relative to each other.

In particular in the case of a mixture in which the homogeneous distribution of particles differing from each other is important, the particle system according to the invention ensures that this distribution is stabilized.

“Measure” within the terms of the invention means any physical and/or chemical parameter which furthers a segregation of the particle mixture. In particular, this is the shape, the weight, the size, the density, the electrostatic charge and/or the surface roughness of the particles.

In the case that for example particles of different sizes are mixed homogeneously, these particles will be arranged by jarring movements of the container in such a way that smaller particles migrate toward the bottom of the container, and the bigger particles accumulate on the top. Without any counter measures, the result when viewing the total amount is thus an inhomogeneous distribution of the particles of different sizes.

Also particles which differ in regard of weight or of surface roughness exhibit a similar segregation tendency, i. e. heavier or smoother particles tend to move toward the bottom of the container in comparison to the lighter or rougher particles.

In addition to powdered particles, the invention also relates to dispersed particles. These particles are preferably powdered particles. Particularly preferably they are pigments. Very particularly preferably the particle mixture comprises luminescent substances.

Advantageously, the luminescent substances are inorganic substances such as rare-earth doped host lattices, such as described in WO 2002/070279.

In particular the luminescent substances are a mixture of chemically and/or physically differentiable luminescent substances. The substances are chemically and/or physically differentiable e. g. if they have different chemical formulas, different lattice structures or different spectra.

In an embodiment according to the invention a coding is produced on the basis of the differentiability of the particles in the mixture. This coding can for example be based on the presence or absence of certain substances or also on the different concentration ratios within the mixture. It is also conceivable to produce the coding on the basis of the spectral properties of the different substances.

For the particles preferably D₉₉<50 μm, particularly preferably D₉₉<20 μm, applies. In particular it applies for the particles to be incorporated in paper that D₉₉<20 μm, and for particles which are to be used in printing that D₉₉ is 6 to 10 μm.

The container is a typically used transport container for free-flowing cargo. These are for example plastic drums, metal drums, plastic sacks, etc.

According to the invention the container has at least one means which essentially prevents the spatial movement of the particles relative to each other. This means that the particles in the mixture do not change their spatial arrangement in relation to each other, in particular this means that the means essentially prevents a segregation of the particle mixture or stabilizes a homogeneous distribution of the particles in the mixture.

In an embodiment according to the invention the means produces overpressure or underpressure in the container in which the particles are disposed. Preferably, a suitable valve is used for this purpose. For producing overpressure preferably a pressure cushion is inserted in the container.

Alternatively it is possible according to the invention to divide the particle mixture into partial amounts and to separate those by suitable means.

The means for a spatial separation of the partial amounts are e. g. several separate packaging units, in which the partial amounts are each packed individually. As separate packaging unit e. g. small plastic sacks, in which the mixture is sealed, can be used.

Alternatively the particle mixture can also be filled into a tubular structure. This structure is placed in the container in a meandering shape. This structure preferably additionally has separate chambers and optionally a pull thread.

In an alternative embodiment at least one partition bottom and/or a partition wall is disposed in the container, thereby restricting the freedom of movement of the particles. The more partition walls and/or partition bottoms are used, the stronger the freedom of movement of the particles is restricted and hence the segregation is prevented.

In a further embodiment according to the invention an adhesive, preferably a water-soluble adhesive, is used as means to press the particles along with the adhesive so as to form a granulate material. Optionally the adhesive can be additionally activated by a temperature treatment. The dimensions of the pressed granular material are preferably in a range of 1 to 5 cm. Instead of the adhesive also a water-soluble PVA paste can be used. In a particularly preferred variant an additive is added, which disintegrates under the generation of gas upon contact with solvents and thus facilitates the dissolution of the granular material. For example NaHCl3 can be used for this purpose.

As a further alternative, instead of pressing, the particles can also be extruded into a polymer, preferably a water-soluble polymer.

It is also conceivable to incorporate the particles in a paste for stabilizing the mixture.

According to the invention also a method for producing an inventive particle system is provided.

Further embodiments and advantages of the invention will be explained in the following with reference to the Figure. The proportions shown in the figure do not necessarily correspond to the relations existing in reality and serve mainly to improve clarity.

The figures are described as follows:

FIG. 1 Particle mixture with container according to the state of the art in cross section,

FIG. 2 to 4 particle systems according to the invention in cross section,

FIG. 5 a, b connection elements,

FIGS. 6 and 7 particle systems according to the invention in cross section.

FIG. 1 shows a transport container 4 which was filled with a particle mixture 1 of big and small particles 2, 3. The container was already transported, to that the particles of different sizes were already subject to a segregation effect due to jarring movements. The initially homogeneous mixture now exhibits an irregular distribution of the different particles, so that at the customer a regular distribution of all particles throughout the total amount delivered is no longer given. Typically the containers, such as the transport container, have a volumetric capacity of 200 l, preferably of 100 l, particularly preferably of 50 l. The delivered amounts of particles typically range between approximately 10 and 100 kg.

FIG. 2 shows a particle system 5 according to the invention, which consists of the container 6 and several separate packaging units 7 with the particles disposed therein (not shown). In the present case the separate packaging units are small plastic sacks which were filled with the particle mixture freshly produced by the producer and sealed. The small sacks are particularly suitable for packaging statically chargeable particles or highly viscous dispersions. The filled small plastic sacks are then stacked into the container 6. Optionally, the small sacks are equipped with a valve including a dust filter. This has the advantage that during the stacking, air is pressed out of the small sacks below by the weight of the small sacks disposed above, the sacks thus come to lie more densely and the space can thus be used more effectively. During the transport from the producer to the customer the small sacks restrict the freedom of movement of the particles in the container, so that a segregation can essentially be prevented. Furthermore, the small sacks have the advantage that the particle mixture is easier to handle and also dosage is facilitated by the packaging in portions. Preferably the small sacks are water-soluble, so that a tearing open and emptying of the small sacks is unnecessary. As an alternative to the completely water-soluble small sacks, there is also the possibility to use a water-insoluble small sack with a water-soluble seam and air cushion. In use the seam dissolves, the particles are set free, the insoluble small sack swims on the surface of the solution or dispersion and can be fished out. The water-insoluble packaging units consist e. g. of polymer foil, such as PE, PP, PVC. The water-soluble packaging units consist e. g. of PVA foils or carboxymethyl cellulose foils. Also packaging units of paper, optionally coated, paper compounds, cloth, etc. are thinkable.

The packaging units preferably have a capacity of approx. 100 g to 5 kg particles. The number of packaging units depends on the size of the container, but should preferably be chosen in such a way that the space of the container is filled as completely as possible.

FIG. 3 shows a further particle system 8 according to the invention, which consists of the container 9 and a tubular structure 10 with the particles disposed therein (not shown). The structure 10 is filled with the particle mixture freshly produced by the producer and is placed in the container in a meandering shape. At the bends of the tubular structure a kind of natural barrier for the particle mixture is created, so that also here the freedom of movement of the particles in the container is restricted. Additionally, webs 11 can be incorporated in the inside of the structure, so that the structure is divided into individual chambers. For emptying the structure, the structure only has to be removed from the container, so that the particle mixture can be poured out through an opening at one end of the structure. In the case that less freely flowing particle mixtures are used, the structure can also be cut open or be torn open by means of a pull thread incorporated longitudinally. The tubular structure preferably consists of PE, PP or PVC. Also all further materials, as described under FIG. 2 concerning the separate packaging units, are thinkable. Preferably the tubular structure has a diameter between 5 up to 20 cm and is approximately 3 m long. The dimensions can of course be varied in dependence of the containers and particles used.

FIG. 4 shows a further particle system 12 according to the invention, which consists of the container 13 and partition bottoms and partition walls 14, 15 with the particles disposed therein (not shown). Of course it is also possible to use only partition walls or only partition bottoms. In the case that only partition bottoms are used, in the filing of the container first a layer of mixture is filled in, the partition bottom is placed on top, another layer of mixture is filled in and a partition bottom is inserted. This procedure is repeated for such a time until the container is filled completely. In the case that only partition walls are used, these should already be installed in the container before filling. The partition bottoms or partition walls can for example consist of metal, plastic, cardboard, etc. Preferably the partition elements are reusable or at least recyclable. The volumes divided off by the partition bottoms and partition walls preferably amount to approximately 103 cm³. The adjustment of the partition elements and the correspondingly divided-off volumes can also be adapted in dependence of the dimensions of the removal tool, in the case that it is not desired to empty the container completely. In this case the volumes are preferably adjusted in such a way that at least one volume unit is seized by the removal tool.

FIG. 5 a shows an example of a partition wall in the form of a connection element. FIG. 5 b shows three connection elements already fit into each other. It is of course possible to use any desired number of connection elements, so that the connection system can be adapted to any container size.

The simultaneous use of partition bottoms and partition walls is most advantageous. In this case the filling is carried out in such a way that first a layer of connection elements, as schematically shown in FIG. 5 b, is installed on the bottom of the container. The number of connection elements depends on the length and width of the container. A determined amount of the particle mixture is then filled into the container. The amount should be determined in such a way that the fields limited by the connection elements are filled up to the upper edge of the connection elements. Afterwards the elements are covered by a partition bottom. On top of this another layer of connection elements is placed, and the above procedure is repeated. The procedure is preferably repeated for such a time until the container is filled. In the emptying of the container the total content can simply be transferred to another container and the connection elements can be removed from the mixture. The connection elements can optionally even be reused.

FIG. 6 shows a further particle system 16 according to the invention, which consists of the container 17, a container cover 18 with valve 19, a pressure cushion 20 and the particles 21 disposed therein. After the filling in of the freshly produced particle mixture and locking of the container cover 18 the pressure cushion 20 is inflated via the valve 19 and the mixture is thus compressed. This is a very simple, technically easy to be realized construction, which does not require any considerable financial expenditure.

In a variant which is particularly easy to realize the pressure cushion 20 and the valve 19 can be omitted. In this case the restriction of the freedom of movement of the particles is achieved by filling the container 17 up to its edge and closing the container cover flush with the edge. Within the container there is thus preferably no free space which would allow the particles to move.

FIG. 7 shows a further particle system 22 according to the invention, which consists of a double-walled container 23 with an elastic inside lining 24, a pressure valve 25, an air escape valve 26 and the particles 27 disposed in the container. After filling the mixture into the container the double wall is pumped up via the pressure valve 25 and the content is pressed from all sides. Via the air escape valve 26 possibly occurring overpressure is relieved. Optionally via the air escape valve additionally an underpressure, preferably a vacuum, can be created inside. Alternatively it is also possible to close the pressure valve 25 and to create a vacuum on the inside of the elastic inside lining 24 via the air escape valve. Highly fluid particles, i. e. electro-statically strongly charged particles, can optionally be discharged after the filling in by e. g. a so-called “ion blower”. 

1. Particle system, comprising a container and a particle mixture for protection against forgery disposed in the container, wherein at least a part of the particles in the mixture differs from the rest of the particles in regard of one measure, and wherein the container includes at least one means for preventing the spatial movement of the particles relative to each other.
 2. System according to claim 1, wherein the means essentially prevents a segregation of the particle mixture.
 3. System according to claim 1, wherein the means stabilizes a homogeneous distribution of the particles in the particle mixture.
 4. System according to claim 1, wherein the particles are pigments.
 5. System according to claim 1, wherein the particles form a coding.
 6. System according to claim 5, wherein the coding is based on the mixture ratio of the particles in the mixture.
 7. System according to claim 1, wherein the particles comprise luminescent substances.
 8. System according to claim 1, wherein the measure is of at least one of the size, the shape, the weight, the density, the electrostatic charge and the surface roughness.
 9. System according to claim 1, wherein the means is adapted to produce overpressure or underpressure in the container.
 10. System according to claim 1, wherein the means comprises a pressure cushion disposed in the container.
 11. System according to claim 1, wherein the means for producing overpressure or underpressure comprises a suitable valve.
 12. System according to claim 1, wherein the particles are packaged as densely as possible.
 13. System according to claim 1, wherein the particle mixture is divided into partial amounts and the means is adapted to spatially divide the partial amounts.
 14. System according to claim 13, wherein the means comprises several separate packaging units in which the partial amounts are respectively packaged.
 15. System according to claim 1, wherein the means comprises a tubular structure arranged in a meandering shape.
 16. System according to claim 15, wherein the tubular structure includes a pull thread.
 17. System according to claim 1, wherein the means comprises at least one of a partition bottom and a partition wall.
 18. Method for producing a particle system including a container and a particle mixture for protection against forgery disposed in the container, wherein at least a part of the particles in the mixture differs from the rest of the particles in at least one measure, comprising the steps: equipping the container with at least one means which essentially prevents the spatial movement of the particles relative to each other.
 19. Method according to claim 18, including using as said means an arrangement to cause overpressure or underpressure in the container.
 20. Method according to claim 19, wherein the overpressure is produced by a pressure cushion.
 21. Method according to claim 19, wherein the overpressure or underpressure is produced by a suitable valve on the container.
 22. Method according to claim 18, including producing a vacuum in the container.
 23. Method according to claim 18, including dividing the mixture into partial amounts and using as such means an arrangement that spatially divides the partial amounts.
 24. Method according to claim 23, including using as said means several separate packaging units in which the partial amounts are respectively packaged.
 25. Method according to claim 18, including using as said means a tubular structure arranged in a meandering shape.
 26. Method according to claim 18, including using as said means at least one of a partition bottom and a partition wall. 